1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing method, and a storage medium. In particular, the present invention relates to a technology suitable for use in preventing data of a print job from being falsified when the print job is transmitted from an information processing apparatus such as a personal computer to, for example, an image processing apparatus such as a printer through a network.
2. Description of the Related Art
Conventionally, on a system in which print data is printed by sending the print data from an information processing apparatus, such as a client personal computer, to an image processing apparatus, such as a printer, through a network, there is a potential threat in which the print data can be falsified on the sending path. FIG. 1 illustrates the concept of a network printing system having the threat. As shown in FIG. 1, when print data is sent from a print client 101 to a network printer 102 through a network 104 such as a local area network (LAN), an attacker 103 (e.g., a personal computer in which a printer driver is installed) can falsify the printing result by intercepting the print data in the middle of data sending by using a technique such as fabricating the network address of the network printer 102, falsifying the print data, and sending the falsified print data to the network printer 102.
Conventionally, in order to cope with the above threat, regarding prevention of falsification of not only a print job but also data, it is common to check data for falsification such that, after a data generating end calculates a hash value of the entire data by using a hash function, the data generator adds an electronic signature to the hash value, a data verifying end verifies the electronic signature. Regarding prevention of falsification of the print job on the network 104, a checking method using a similar technique has been disclosed (see, for example, Japanese Patent Laid-Open No. 2003-084962).
FIG. 2 is a schematic illustration of calculation of a hash value. At first, after print data 201 is generated, its hash value 202 is calculated, and transmitting data (d1) 203, obtained by adding the hash value 202 to the print data 201, is created. The hash value 202 can be obtained by inputting the print data 201 to a known hash function such as a one-way function such as SHA-1 (Secure Hash Algorithm 1) or MD5 (Message Digest 5).
When receiving the transmitting data (d1) 203, the network printer 102 calculates a hash value from the print data 201 in the received data, and confirms whether the calculated hash value coincides with the hash value 202 included in the transmitting data (d1) 203. This can determine whether or not the print data 201 has been falsified on the network 104.
However, in the case of verifying, using the above method, whether the print data is correct or not, the client PC calculates a hash value after completing generation of all print data, and then sends a network printer the print data. Further, the network printer verifies the hash value after completing reception of all the print data, and then starts a printing operation. This causes a problem in that the start of printing, which is the so-called “first printing”, is delayed. This problem notably occurs particularly when print data has an amount reaching several hundred pages.